There’s big and there’s big. “It was one of the largest movements of material ever to occur on our planet,” says Peter Talling of the University of Bristol (press release), putting the underwater landslide he and his colleagues have been studying off the coast of Africa firmly in the second category. “This mass was ten times that transported to the ocean every year by all of the Earth’s rivers. The flow was sometimes over 150 km wide, spread across the open sea floor.”

An analysis by Talling and his colleagues in this week’s Nature shows that the flow, which occurred thousands of years ago, extended 1,500 kilometres and carried 225 billion tonnes of sediment.

Bizarrely, the flow travelled hundreds of kilometres before it started to deposit any sediment. Only when it encountered a minute change in gradient on the ocean floor did it start ditching billions of tonnes of material. Although the change of gradient was abrupt its miniscule size is startling – from 0.05˚ to 0.01˚.

Coverage

The “mother of all mudslides”, in the Daily Telegraph

“The massive surge put down the same amount of sediment that comes out of all the world’s rivers combined over a period of 10 years”, from the BBC